Fasteners are well known in the art. Often fasteners may loosen as a result of vibration or thermal expansion. To alleviate this problem, a wide variety of lock washers have been developed in the art. Lock washers attempt to prevent loosening by increasing the frictional forces between the nut and a stationary surface. Some examples include, a split ring lock washer, a star lock washer, or spring washers. Although these types of lock washers inhibit rotation of the nut by increasing the frictional forces acting opposite to the nut's rotation, they do not provide a positive rotation stopping force.
In a similar manner, nylon inserts have been used to constrict the internal diameter of the threads on the exit side of the nut. Again, these inserts increase the frictional forces, in this case between the bolt and nut threads, that act to resist rotation of the nut. Alternatively, it is known to simply crimp the nut to increase rotational friction. As in the case of lock washers, these methods of increasing the rotational friction do not provide a positive stopping force against rotation of the nut. In addition, nylon inserts are more susceptible to deformation caused by excess heat or corrosive agents.
One known device for positively stopping nut rotation is the castle nut. The castle nut has a crenelated upper surface that may be used to positively stop rotation of the nut. To accomplish this, the nut is tightened to its desired level and then, a hole is drilled through the bolt in a gap between the nut's crenelations. A cotter pin is then passed through this hole and secured in place. In this way, the nut cannot rotate or loosen because the pin provides a positive stop. Unfortunately, the castle nut requires customized placement of the pin to prevent rotation. In other words, the user must drill a hole through each fastener on which the castle nut will be used. The positioning of the hole along the length of the bolt will depend on the thickness of the parts being joined, the number of washers, and the desired tightness. Consequently, the castle nut is rendered job specific preventing it from being mass produced and having universal application. Moreover, any adjustment of the nut would require drilling a new hole.
Therefore, a need exists for positive locking fastener that prevents loosening of a nut brought on by vibration. A need also exists for a positive locking fastener that may be mass produced and applied universally. A further need exists for a positive locking fastener that can move to more than one location along the bolt shaft without having to remodify the bolt.